The tools to install a fork are hardly complicated. I think just a pipe cutter and a file would do it. Something to hammer in the star-fangled nut.

The rigid forks available for MTB’s are really heavy duty. They’re not 531SL. They depend on large, quality tires, aired down, to make a good ride. Like gravel bikes but worse. It’s not a path I’d take except with plus tires on maybe a SS